Laryngeal Hemiplegia in Horses
Definition:
Laryngeal Hemiplegia (Recurrent Laryngeal Neuropathy): Progressive neuropathy of the recurrent laryngeal nerve, leading to dysfunction of the cricoarytenoideus dorsalis muscle and arytenoid cartilage paralysis.
Causative Agents:
Primary Cause: Axonal dystrophy of the recurrent laryngeal nerve.
Secondary Causes: Trauma, guttural pouch disorders, chemical intoxication, lead toxicity.
Symptoms and Clinical Changes:
Primary Signs: Inspiratory noise (whistle or roar), poor performance, exercise intolerance.
Secondary Signs: Prominent arytenoid cartilage due to muscle atrophy.
Diagnostics:
Clinical Evaluation: Inspiratory noise, poor performance.
Endoscopic Evaluation: Reduced or absent arytenoid abduction; Havemeyer grading system (Grade 1-4).
Laryngeal Ultrasonography: Changes in echogenicity of laryngeal muscles.
Differential Diagnoses:
Arytenoid chondritis, nasopharyngeal collapse, axial deviation of aryepiglottic folds.
Treatment:
Conservative Treatment: Monitoring for non-exercise intolerant horses.
Surgical Treatments:
Prosthetic Laryngoplasty (Tie-back): Permanent arytenoid abduction to enhance airflow.
Ventriculectomy/Sacculectomy: Removal of laryngeal ventricle mucosal lining.
Ventriculocordectomy: Removal of vocal fold and laryngeal ventricle mucosa.
Laryngeal Reinnervation: Neuromuscular graft for young horses with partial paralysis.
Partial Arytenoidectomy: For recurrent cases or prosthetic laryngoplasty complications.
Mechanism of Action:
Prosthetic Laryngoplasty: Mimics function of the cricoarytenoideus dorsalis muscle, prevents airway collapse.
Ventriculectomy/Ventriculocordectomy: Reduces noise during respiration.
Reinnervation: Restores neuromuscular function to laryngeal muscles.
Key Points:
Laryngeal hemiplegia often affects the left side.
Diagnosis through endoscopy and ultrasonography.
Treatment tailored to severity and intended use of the horse.
For detailed information, visit the Merck Veterinary Manual.
